Apparatus for heating a viscous liquid

ABSTRACT

An open ended tubular heating unit is provided which is comprised of a stainless steel tube surrounded by an induction heating coil which is disposed in magnetically coupled relationship with the tube. The tube and coil are encapsulated in insulating material, and the unit is submersible in a viscous liquid such as oil which is disposed in a vessel and the temperature of which liquid inhibits pumping thereof from the vessel. The unit is adapted to be supported in suspension and the coil energized to inductively heat the stainless steel tube, whereby the liquid inside and surrounding the unit is heated to elevate the temperature thereof and reduce the viscosity thereof. A driven impeller may be provided within the tubular unit to impel liquid flow therethrough, and a driven pump may be provided within the unit to pump the heated liquid from the vessel.

[11] 3,824,364 [451 July v16, 1974 2,881,301 4/1959Bowman....................,.,.. 3,031,106

[54] APPARATUS FOR HEATING A VISCOUS 4/1962 H0oker...........

LIQUID 3,053,959 9/1962 Christmann.........fff..........219/1o.49

[75] Inventor: John F. Cacliat, Cleveland, Oliio Assignee: Park-OhioIndustries, Inc., I

Primary Examiner-A. Bartis Cleveland, Ohio Attorney, Agent, 0rFirm-Meyer, Tilberry & Body a w mm APPARATUS FOR HEATING A VISCOUSLIQUIDThe present invention relates to the art of induction heating and, moreparticularly, to a device for elevating the temperature of a viscousliquid to facilitate pumping thereof.

Viscous liquids such as oil are often stored in tanks and other vesselswhich are exposed to temperature conditions which lower'the temperatureof the oil to the extent that free pumping of the oil is most difficult,if at all possible. For example, a vessel such as an oil tanker isadapted to store thousands of gallons of oil for transportation from onelocation to another across a waterway. Water and/or air temperatureconditions can cause the oil temperature to drop during thetransportation period to a level which inhibits freepumping of the oilfrom the vessel when it reaches its destination. Temperature conditionsin cold climates and during winter months can similarly affect oilcontained in storage tanks and the like. Further, in the event that avessel such as an oil tanker sinks before reaching its destination, itbecomes desirable to salvage the oil carried therein. While the airand/or water temperatures on the surface vmay not have an undesirableaffect on the viscosity of the oil, the temperature of the water at thedepth of the sunken vessel is likely to be sufficiently low to adverselyeffect the viscosity.

To achieve free pumping of the oil under such conditions it is necessaryto elevate the temperature of the oil in order to lower the viscositythereof. lt has been the practice heretofore to use steam to raise thetemperature of the oil so that it can be freely pumped. The use of steamtogether with the necessary devices and arrangements for transmittingthe steam to the vessel entails considerable expense both in time andcost of equipment. Further, once the temperature of the oil has beensufficiently elevated to enable pumping thereof, such pumping must beachieved by apparatus separate from that employed to generate and directthe steam to the oil vessel. It will be appreciated, therefore, that thepumping of oil from a vessel or the salvaging of oil from a sunkenvessel in accordance withprior practices is at best a cumbersomeoperation.

ln accordance with the present invention, a device is provided whichenables a moreexpeditious and economical heatingof viscous liquids in avessel to elevate the temperature thereof to a level at which the liquideffort and in a minimum amount of time. More particuv larly, the deviceis adapted to be lowered such as by a support cable into the vessel andsubmerged in the liquid, and once so disposed the device is ready foroperation.

Basically, the device of the present invention is tubular and comprisedof an inductively heatable metal tube submersible in the liquid and openat its upper and lower ends to provide for liquid flow therethrough. Inaccordance with one aspect of the present invention, the liquid withinand immediately surrounding the tube is heated to elevate thetemperature of the liquid. Convection current flow causes the heatedliquid in the tube to rise and flow out the upper end thereof and colderliquid to enter the lower end of the tube.

In accordance with another aspect of the present invention, a motordriven impeller is disposed within the tube to facilitate circulation ofliquid through the tube from one end thereof to the other. Such forcedcirculation of heated liquid from one end of the tube and cold 'liquidinto the other endof the tube enables the pro- Inaccordance with apreferred embodiment, the tube is cylindrical and is stainless steel.The tube is surrounded by an induction heating coil which is disposedinvmagnetically coupled spaced relationship with respect to the tube.The tube .and coil are encapsulated in insulating material and theresulting tubular unit is adapted to be suspended in the liquid with itsaxis extending generally vertically. A support cable arrangement or thelike is provided at one end of the tubular unit to facilitate raising,vand lowering the unit into the vessel. The support cable extends to aworking location remote from the vessel and at which location the powersupply for the coil and other operating equipment for the unit isdisposed. It will be' seen, therefore, that the heating device .canreadily be elevated and lowered with respect to a liquid vessel and thatnothing more is required to place the device in readiness for operationbeyond locating the device in the liquid vessel.

An outstanding object of the present invention is the provision of aninduction heating device submersible in a viscous liquid and operable toelevate the temperatureof the liquid to a level which enhances pumpingof the liquid from the vessel.

Another object is the provision of an induction heating device of theforegoing character which is adapted to be lowered into and raised froma liquid vessel from a location remote from the vessel and controlledfrom the remote location to facilitate the heating and circulating ofliquidin the vesselv relative thereto.

A further object is theprovision of a device of the foregoing characterwhich is of tubular construction yto facilitate the flow of liquidtherethrough and which is provided .with a driven impeller to impelliquid flow therethrough.

Still another object is the provision of a device of the foregoingcharacter which is provided with a pump for pumping the heatedliquid'from the vessel to the remote location. y

Yet another object is the provision of a device of the foregoingcharacter which enables the heating and removal of viscous liquid from avessel in a more expeditious and economical manner than heretoforepossible.

The foregoing objects, and others, will in part be obvious and in lpartmore fully pointed out hereinafter in conjunction with the descriptionof the accompanying drawing wherein preferred embodiments of theinvention are depicted, and in which:

FIG. 1 is a sectional elevation view of a heating device made inaccordance with the present invention;

FIG. 2 is a cross-sectional-view of a preferred conductor 4arrangementfor transmitting power to the induction heating coiliof the device, thevsection being .along line 2 2 in FIG. 1;

. cable can be elevated and lowered from such location wherein theshowings are for the purpose of illustrating preferred embodiments ofthe invention only and not for the purpose of limiting the invention, aheating device is illustrated in FIGS. 1-3 which is comprised of a metaltube 12 surrounded by an induction heating coil 14. Preferably, tube 12is cylindrical and is a stainless steel tube having an outer diameter ofapproximately ten inches and a wall thickness of approximately l inch.Coil 14 is insulated from tube l2 by suitable refractory insulatingmaterial 16 which is non-flamable and capable of withstandingy atemperature of atleast 1,000F.' Any suitable refractory Y insulatingmaterial y can be used, one suitable material being glass impregnatedmica. Preferably, both coil 14 and tube 12 are embedded in insulatingmaterial 16 in a manner l whereby the inner and outer surfaces of theheating device and the opposite ends thereof are vdefined by suchinsulating material.

Heating device 10 is adapted to be lowered and raised relative to avessel in which viscous liquid to be heated is disposed. Such a vesselis not illustrated, but it will be appreciated that the vessel will haveor will be provided with an .opening of sufficient size for the heat'-ing device to be introduced and removed from the vessel. Heating device10 is adapted to be displaced relative to such a vessel by a supportcable arrangement interconnected with the heating device in any suitablemanner. In the embodiment illustrated in FIG. l, one end of the deviceis provided with a metal support plate 18 including a central portion 20and legs 22 extending radially therefrom and having outer ends extendingthrough insulating material 16 and suitably interconnected with tube 12.Suchin'terconnection can, for example, be defined by riveting the outerends of legs 22 to tube 12 and, preferably, insulating plates 23 aredisposed between the legs and tube to thermally insulate support plate18 from tube 12. Legs 22 are each provided with lan eyelet component 24adapted to be interconnected with a suitable support cable arrangementsuch as that provided by cables 26 in the embodiment illustrated in FIG.l. Cables 26 can be connected together at a point axially spaced fromthe end of the such as by hand, or by a winch or the like provided atthe remote location. The remote location may be defined, for example, bya platform adjacent a liquid storage tank, or by a recovery ship in theevent that the liquid to be heated is disposed in a submerged vesselsuch as an oil tanker'. Further, such remote location might be definedby a dock or the like at which a vessel such as an oil tanker is dockedfor unloading. In any event, it will be appreciated that the heatingdevice when disposed inthe vessel containing the viscous liquid will bespaced a considerable distance from the remote location from which thedevice is manipulated.

The power'supply 42 for energizing the coil will also be located at theremote location and thus will be considerably spaced from the heatingdevice. Anysuitable alternating current power supply may be provided atthe remote location for the purpose of energizing the coil. In order toreduce line losses in delivering power to coil 14, the coil and powersource preferably are interconnected by a lplurality of flexibleconductors connected transversely with respect to one another. In theembodiment illustrated, end 30 of coil 14 is connected by couplingdevice34 to a pair of conductors 38 and, similarly, end 32 of coil 14 isconnected by coupling device 36 with a pair of flexible conductors 40.The pairs of conductors 38 and 40 extend from heating device l0 to acommon juncture such as the point at which cable 28 is connected tocables 26. At this point conductors 38 and 40 extend parallel to oneanother along cable 28 and are arranged as illustrated in FIG. 2. Moreparticularly, conductors 38 are of one polarity and conductors 40 are ofthe opposite polarity. The specific arrangement illustrated in FIG. 2provides forreducing line losses in transmitting current from powersource 42 at the remote location to coil 14. It will be appreciated thatpairs of conductors 38 and 40 will be separated at the remote locationfor connection of correspending ones of the pairs of conductors toopposite sides of power supply 42. y

Heating device 10 as thus far described is adapted to be lowered into avessel containing viscous liquid such as oil which is ata temperaturebelow that at which the oil can be readily pumped. The device issupported in the vessel with its axis in a generally verticaldisposition. Once the heating device is submerged in the liqheatingdevice by a single cable 28 extending to the remote location from whichthe heating device is raised and lowered relative to the vessel in whichit is to be employed. u

Coil 14 preferably is a continuous conductor of solid cross sectionhaving convolutions l5 axially vspaced apart along the length of tubel2. The coil includes end portions 30 and 32 provided with couplingdevice 34 and 36, respectively, for connecting the coil with a suitablesource of alternating current, as set forth more fully hereinafter. Coilends 30 and 32 extend through corresponding openings in tube 12, whichopenings are lined with sleeves 33 of insulating material.

Support cable28 extends from heating device l0y to a remote location andit will be appreciated that the uid, coil 14 is energized from powersupply 42 and the current flowing through the coil causes steel tube 12to be inductively heated. Theheat from tube 12 is conducted to theviscous liquid within and surrounding de vice l0, whereby thetemperature of the liquid is elevated. As the temperature of the liquidincreases, the

liquid will circulate in a well known manner by convection, whereby thewarm liquid will move upwardly through the tubular unit and colderliquid will enter the lower end of the unit, as indicated by the arrowsin FIG. 1. In this manner, the temperature of the liquid in the vesselis 'gradually increased in that the warmer liquid rises in the vesseland the colderliquid descends therein.

The extent to which the entire volume of liquid in a given vessel can beheated to elevate the temperature thereof to the desired level depends,of course, on the size of the vessel, the surrounding temperatureconditions and the extent to which circulation of the liquid relative tothe heating device is achieved. Accordingly,

.it may be ,desirable in certain instances to provide v means withinthe. heating device to positively circulate liquid therethrough so as toincrease the amount of liquid that can be heated'during a given periodof time. Such positive circulation of the liquid is also advantageous inassisting the transfer of heat from the metal tube to the liquid. Anysuitable liquid circulating arrangement may be provided for this purposeand, in the embodiment illustrated in FIG. 1, such circulation of theliquid is achieved by a motor driven impeller disposed within heatingdevice 10.

As illustrated in FIG. 1, the motor driven impeller bodimentillustrated, the pump is a centrifugal pump in which impeller 62receives fluid centrally thereof and displaces the fluid in a radialdirection. The pump has an inlet opening 66 for fluid within the heatingdevice and an outlet 68 extending through a suitable opening therefor insupport plate 18. The pump is mounted on unit includes a rotatable blade44 mounted on the drive shaft of electric motor 46. It will beappreciated that motor 46 is potted or otherwise made fluid tight andimpervious to the liquid to be heated. Motor 46 is supported by supportplate 18 and, for this purpose, the housing of the motor may be suitablyinterconnected with center portion 20 of plate 18 such as by a pluralityof studs 48 extending through corresponding apertures in center portion20 and into threaded engagement with apertures in the motor housing.Preferably, the motor housing is insulated from support plate 18 such asby interposing a plate S of insulating material between the motorhousing and support plate. Motor 46 is adapted to be energized through aconductor 52 extending from the motor to the remote location forinterconnection with a suitable power supply therefor. Motor 46 may beoperated intermittently or continuously to rotate impeller 44 to impelliquid through the heating device from one end of tube 16 toward theother. Moreover, the rate at which the liquid is impelled through theheating device by impeller 44 can be controlled such as by intermittentoperation of the motor or, for example, by providing for motor 46 to'bea variable speed electric motor. If theheating device is suspended inthe liquid so that 4the axis-of the metal tube l2 is substantiallyvertical, it is preferred to provide for the impeller to move the liquidthrough the heating device from the lower end thereof toward the upperend thereof so as to supplement the aforementioned flow of liquid byconvection through the heating device.

When heating device l0 is employed either alone or in conjunction with afluid circulating impeller, the liquid in the vessel is heated toelevate the temperature thereof to a level which provides for the liquidto be readily pumped from the vessel. Such pumping can be achieved by asuitable pump unit introduced into the vessel independently of theheating device. Heating device 10, however, advantageously provides forpumping to be achieved by a pump unit physically associated with theheating device, thus to eliminate the necessity of introducing twoseparate units into the vessel to achieve heating and removal of theliquid from the vessel. Such a heating and pumping arrangement isillustrated in the embodiment of FIG. 4, wherein a heating unit isdepicted which corresponds in structure to the heating unit illustratedin FIG. l. Accordingly, like numberals are used in FIG. 4 to designatecomponents of the heating device corresponding with the 'components ofthe device in FIG. 1.

In the embodiment illustrated in FIG. 4, a pump 60 is mounted on supportplate 18 in place of the motor driven impeller. Pump 60 includes animpeller 62 disposed within the pump housing and adapted to be driven bya motor 64 disposed within the housing. Any suitable pump device may beemployed and in the ernuid from the vessel to any desired destinationpoint `such as the remote location.

o As in the embodiment illustrated in FIG. l, the energization ofinduction heating coil 14 inductively heats steel tube 12 to heat theviscous liquid in the vessel and cause circulation thereof by convectionthrough the heating device in the direction of the arrows in FIG. 4.

' When pump motor 64 is energized, impeller 62 is rotated to draw heatedliquid within the heating device into the pump and through outlet 68 toconduit 72 leading to the delivery location.l Accordingly, theembodiment illustrated in FIG. 4 provides a unitary heating and pumpingdevice which enables the temperature of the viscous liquid to beelevated sufficiently for the liquid to be freely pumped and for theheated liquid to be pumped from the vessel. In order to coordinate thepumping rate with the heating rate of the heating device, motor 64 maybe operated intermittently or may be a variable speed electric motor.

In the embodiment illustrated in FIG. 4, operation of pump 60 will tosome extent induce liquid flow through the heating device from the lowerend thereof toward the upper end thereof by the suction created at thepump inlet. This induced flow supplements the circulation of liquidresulting'from flow thereof by convection. While circulation of theliquid by convection and induced flow may be adequate, it'may bedesirable in certain instances'to supplement the liquid flow by apositive circulating device in order to increase the rate at which theliquid is heated and accordingly the rate at which it can be pumpedfrom'the vessel.

An arrangement suitable for the foregoing purpose is illustrated in theembodiment of FIG. 5 of the drawing. In FIG. S, heating device 10corresponds in structure to the heating devices illustrated in FIGS. 1andv 4, whereby like numerals are employed in FIG. 5 to designatecorresponding components of the heating device. In the embodimentillustrated in FIG. 5, heating device 10 is provided with both a liquidpump and a liquid impeller unit. More particularly, a motor-pump unit ismounted on support plate 18 in a manner similar to that describedhereinabove in connection with the motor and pump units in FIGS. l and4. Motor-pump assembly 80 includes a pump 82 and a drive motor 84-interconnected as a unit in a well known manner so that the motor, whenenergized, operates the pump. Motor 84 includes a drive shaft 86extending from the lower end'thereof, and an impeller 88 is mounted ondrive shaft 86 for rotation therewith. Pump 82 has an inlet 90 forheated liquid within the heating device and an outlet 92 to which aflexible conduit 94 is attached. Con- :duit-19,4, ofcourse, .leadsipoi'nt forthe liquid, such as the remote location;y

lustrative of the present tion..

Energizati'on of: motor 84 causes liquidg'within .the

I heating device {to be purnpedfrom` the vessel tothe destination pointand causes "liquid ftov bev circulated to av delivery Ior y.destinationi being submersible in `sir-aid liquid, .m eal1` 5. t0 Support lsaiddevice in` saidfliquid froma location remote from said vessel,andmeansfto connect said coil means acrossa throughthe heating device byimpeller'88.j Whilefthe f .pump `'and impeller are illustratedas`4beingdriven by a be-appreciated thatl'where'a ysingle driveniotorfisemployed suitable gear box arrangements'can ybe usedto provide forthe'pumpl and impeller' to be operatedlat different rotationalspeeds.

.t -ln the embodiments described hereinabove, the heating'device issuspended by the support cable within the liquid containing vessel with.the axisiof the heating de- ,vice in a generally vertical disposition.Moreover, the device as llustrated would be suspended abovetliebotjltornfwall-'or the like of the-vesselingorder ,tofacilitate"circulation of the viscous liquid through't'h'e lheating de'- f .sourceof alternating :current 'at saidlocation: for said 'coil meanswhen@energized to inductively heat s aid :tubular, lmerriber to `raise thetemperature of the-liquid.

' 12'.' The .device according 'toclainr l, andfurther in cluding a1motor driven impel-lersupported by said tuspacedfromtheinner surface 'ofsaid passageway to impart movement 'to' Said :liquid from' oneendthereof l, toward the' other, andisupportrnensinterconnecting vice.lt will'be appreciated'however, that in these arrangements the bottom'endof the heating devicecould arrangement'which would venable thevdevice to rest on v be provided with suitable axially extending supportleg saidmoto'r drivenrimpellerfarid said' tubular member. 3; The deviceaccording to claim l,"and furtherincludihg motor driven'pump means'supported by said tubularmernber -withinj saidpas's'ageway, saidpumpmeans being radially spaced inwardly from'the inner surfaceof'saidlpassageway, 'and support means interconnecting lsaid pump.meansand saidtubular'member.

. pump rneansfhas an inleffr'liquidwithin said passageway` and an"outlet, and 'conduit means connected to said outlet for deliveringpumpedl liquid from said vessel. l, 5. The :devicel accordingto-claimA,and a motor driven impeller supported-within said -passagewaygby' thebottom surface of ,a fvesselwithout hindering free heating' device.Further, while considerable emphasisy has been placed hereinonthe `factthat'theheatingdecirculationof the liquidy into the bottom'endof `,they

said ,tubular vmernber to impel liquidlilow through said device, said`rnotort d r'iven impeller being radially spaced inwardly `.from theinner surface `o f said-,passagevice" is supportedwithits axisfinajgenerally vertical dist position to facilitatenatural circulation; ofliquid therethrough. by convection,l it will beap'preciatedthati inthose'embodiments'in which a pu'mp'rand/or' impelleris employed that theheating device could b e4 disposed within theliquidgwith'its axisy ina`generally horizontal disposition. `ln this respect, rthe pumpand/orimpeller providefor circulation of theliquid .through the heating device`to Aachieve l`progressive vheating ofthe liquid in the vessel. It w illbe appreciated to` thatv many suitable 'arrangementsv can be providedfto `achieve support of vthe unit infafhorizontaldisposition, andthat-'many arrangements otherthan the specific support plate `and cablearrangement described herein'fcan' be devisedfor suppo'rtinglthe unitina vertical disposition.

f j-oJn-indiiction device'i'o'r usein recovering a-'viscous' liquidfroma vessel in which the liquid is -at a temperature Whichinhibits-pumping of [the liquid from-thevessel comprising, a singlecylindrical steel tube ,having axially.,oppo sed open upper and lowerends-,ian induction'heat'ing coilsurrounding the exterior of said tubeand-disposed in magnetically coupled relationship therewith, insulating'material enclosing .said coil and tube and'fllling 'the space betweensaid coil and tube, the portion of saidinsulating material withinv saidtube defining anaxialtpa'ss'ageway through said .device,

Asmany possiblelernbodiments of the present invention may be made and asmanypossible changes maybe made in the embodiments hereinillustratedandde- I scribed, it is to be distinctly understood'tha't theforegoing descriptive matter is to be interpreted merely as ilinventionand not as a limital-laving thus described myl'invention, I claim:

l. A tubular induction heating device foruse inrecovering a viscousliquid from a vessel `in which theliquid is at a temperature whichinhibits pumping of the said device'being'Submersible in said liquid,means for supporting said device in' said liquid from a location remot'efrom said vessel and in agenerally vertical disposition, said supportmeans including axially open support arrnmeans extending across saidpassageway and connected tofsaid steel tube adjacent said upper end`thereof,l andmea'nsfor connecting said coil across-a source ofalternating current at said locationfor said coil when energizedtoinductively heat said steel tube liquid from the vessel comprising,alsingle tubular metal member-having axially opposed-open ends,induction heating coil means surrounding the exterior of v said memberbetween said opposite ends and disposed in magnetically coupled spacedrelationship therewith, insulating material enclosing saidcoilfmeans andtubular metal member and tillingthe space between said coil means andtubular member, the portion of said insulating material withinsaid'tubular member defining `an axial passagewaythrough said device,saidldevice l65v f `opening and a liquid outlet, and condult meansconnected to said outlet fordelivering pumped liquid from -to raise thetemperature of liquid within said passageway and promote circulation ofliquid in the direction from said lower end of the tube toward'saidupper end.

.7 The device according to claim 6, and motor driven impeller meansconnected to said support arm'means and -supported in said passagewayadjacent said upper end of said tube to impel liquid'through saidpassageway in said direction.`

t 8. The device according to claim 6, and motor driven I pump meansconnected to said support arm means and supported in said passagewayadjacent said upper end of vsaid tube,l said pumpmeans having a'liquidinlet said vessel. i

passageway in said direction, said pump having an inlet port for liquidand an outlet port, and conduit means connected to said outlet port fordelivering pumped liquid from said vessel.

* =l =l= ik

1. A tubular induction heating device for use in recovering a viscousliquid from a vessel in which the liquid is at a temperature whichinhibits pumping of the liquid from the vessel comprising, a singletubular metal member having axially opposed open ends, induction heatingcoil means surrounding the exterior of said member between said oppositeends and disposed in magnetically coupled spaced relationship therewith,insulating material enclosing said coil means and tubular metal memberand filling the space between said coil means and tubular member, theportion of said insulating material within said tubular member definingan axial passageway through said device, said device being submersiblein said liquid, means to support said device in said liquid from alocation remote from said vessel, and means to connect said coil meansacross a source of alternating current at said location for said coilmeans when energized to inductively heat said tubular member to raisethe temperature of the liquid.
 2. The device according to claim 1, andfurther including a motor driven impeller supported by said tubularmember within said passageway and radially spaced from the inner surfaceof said passageway to impart movement to said liquid from one endthereof toward the other, and support means interconnecting said motordriven impeller and said tubular member.
 3. The device according toclaim 1, and further including motor driven pump means supported by saidtubular member within said passageway, said pump means being radiallyspaced inwardly from the inner surface of said passageway, and supportmeans interconnecting said pump means and said tubular member.
 4. Thedevice according to claim 3, wherein said pump means has an inlet forliquid within said passageway and an outlet, and conduit means connectedto said outlet for delivering pumped liquid from said vessel.
 5. Thedevice according to claim 4, and a motor driven impeller supportedwithin said passageway by said tubular member to impel liquid flowthrough said device, said motor driven impeller being radially spacedinwardly from the inner surface of said passageway.
 6. An inductionheating device for use in recovering a viscous liquid from a vessel inwhich the liquid is at a temperature which inhibits pumping of theliquid from the vessel comprising, a single cylindrical steel tubehaving axially opposed open upper and lower ends, an induction heatingcoil surrounding the exterior of said tube and disposed in magneticaLlycoupled relationship therewith, insulating material enclosing said coiland tube and filling the space between said coil and tube, the portionof said insulating material within said tube defining an axialpassageway through said device, said device being submersible in saidliquid, means for supporting said device in said liquid from a locationremote from said vessel and in a generally vertical disposition, saidsupport means including axially open support arm means extending acrosssaid passageway and connected to said steel tube adjacent said upper endthereof, and means for connecting said coil across a source ofalternating current at said location for said coil when energized toinductively heat said steel tube to raise the temperature of liquidwithin said passageway and promote circulation of liquid in thedirection from said lower end of the tube toward said upper end.
 7. Thedevice according to claim 6, and motor driven impeller means connectedto said support arm means and supported in said passageway adjacent saidupper end of said tube to impel liquid through said passageway in saiddirection.
 8. The device according to claim 6, and motor driven pumpmeans connected to said support arm means and supported in saidpassageway adjacent said upper end of said tube, said pump means havinga liquid inlet opening and a liquid outlet, and conduit means connectedto said outlet for delivering pumped liquid from said vessel.
 9. Thedevice according to claim 6, including a pump, an impeller and drivemeans therefor in said passageway and radially spaced from the innersurface thereof, said support arm means supporting said pump, impellerand drive means within said passageway, said impeller being operable tocirculate liquid through said passageway in said direction, said pumphaving an inlet port for liquid and an outlet port, and conduit meansconnected to said outlet port for delivering pumped liquid from saidvessel.